Extending gex_only option to Visium function

[alexanderchang1]

Extended gex_only function to visium

• Closes Can't read in protein antibody capture data #3113
• Tests included or not required because: It's a straightforward argument pass from visium to read_10x_h5

• Release notes not necessary because: not a big change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.67%. Comparing base (5654389) to head (222c101).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3278   +/-   ##
=======================================
  Coverage   76.67%   76.67%           
=======================================
  Files         112      112           
  Lines       12946    12946           
=======================================
  Hits         9926     9926           
  Misses       3020     3020           

Files with missing lines	Coverage Δ
src/scanpy/readwrite.py	76.88% <100.00%> (ø)

[alexanderchang1]

Hi, I just wanted to follow up on this, we have a project that relies on this functionality that we're hoping to publish in the next two months. I've modified my own version of Scanpy to include this, but I would prefer to be able to just point at a specific version of scanpy in the requirements file when distributing our new package.